1. Field of the Invention
The present invention relates to a method of manufacturing a liquid ejection head, and an image forming apparatus, and more particularly, to a method of manufacturing a liquid ejection head and an image forming apparatus by which an ink droplet is ejected from a nozzle by applying a pressure change to liquid inside a pressure chamber by means of the displacement of a piezoelectric element formed on a diaphragm.
2. Description of the Related Art
Inkjet recording apparatuses perform recording by ejecting ink droplets from nozzles onto a recording medium, while moving a recording head having a plurality of nozzles and a recording medium relatively with respect to each other, and they have come into broad use due to their low noise during the recording operation, their low running costs, and the fact that they enable images of high quality to be recorded onto recording media of various different types. The recording head comprises pressure chambers corresponding respectively to the nozzles, ink flow channels and other components. For example, an ink droplet is ejected from a nozzle connected to a pressure chamber by applying a pressure change to the ink inside the pressure chamber by using a pressure generating device, such as a piezoelectric element, or a heat generating element.
Until now, various methods of manufacturing a recording head have been proposed. For example, Japanese Patent Application Publication No. 2001-191542 discloses a method of manufacturing a recording head which uses a silicon substrate. Japanese Patent Application Publication No. 2001-191542 describes a method in which recess sections are previously formed in the surface of a silicon substrate, these recess sections are buried by SiO2 or the like forming a sacrificial layer, the surface of this layer is leveled and piezoelectric devices are formed by patterning, whereupon the sacrificial layer is removed to obtain pressure chambers. Japanese Patent Application Publication No. 2001-191542 identifies as problems relating to such a method, the large time requirement needed in order to deposit the sacrificial layer, the difficulties in leveling the sacrificial layer, and cost issues. According to Japanese Patent Application Publication No. 2001-191542, in order to resolve these problems, a portion of the surface of the silicon substrate is etched in such a manner that a plurality of column-shaped portions remain, the chemical properties of the plurality of column-shaped portions are modified and a portion of the surface is leveled, a diaphragm and piezoelectric elements are formed on the leveled portion of the surface, and the plurality of column-shaped portions having modified chemical properties are then removed by etching.
However, in the method of manufacture described in Japanese Patent Application Publication No. 2001-191542, the column-shaped portions formed in the prescribed regions of the silicon substrate (the pressure chamber and ink supply port forming portions) are removed by wet etching with HF (hydrofluoric acid) after forming the diaphragm and piezoelectric elements. The column-shaped portions are formed by creating groove sections by etching of the silicon, followed by thermal oxidation, and therefore undulations occur in the bottom face of the pressure chambers and the ejection characteristics are degraded. Furthermore, due to differences in the aspect ratio when forming the groove sections, micro-loading effects occur due to the difference in etching depth (etching rate), and this is liable to give rise to surface irregularities (undulations) and non-uniform depth of the pressure chambers, leading to variation in the ejection characteristics between the nozzles. Accordingly, there is a possibility that the quality of the recorded image may decline.